Smartphones are becoming increasingly indispensable in everyday life for most undergraduates in China, and this has been associated with problematic use or addiction. The aim of the current study was to investigate the prevalence of smartphone addiction and the associated factors in male and female undergraduates. This cross-sectional study was conducted in 2016 and included 1441 undergraduate students at Wannan Medical College, China. The Smartphone Addiction Scale short version (SAS-SV) was used to assess smartphone addiction among the students, using accepted cut-offs. Participants’ demographic, smartphone usage, and psycho-behavioral data were collected. Multivariate logistic regression models were used to seek associations between smartphone addiction and independent variables among the males and females, separately. The prevalence of smartphone addiction among participants was 29.8% (30.3% in males and 29.3% in females). Factors associated with smartphone addiction in male students were use of game apps, anxiety, and poor sleep quality. Significant factors for female undergraduates were use of multimedia applications, use of social networking services, depression, anxiety, and poor sleep quality. Smartphone addiction was common among the medical college students investigated. This study identified associations between smartphone usage, psycho-behavioral factors, and smartphone addiction, and the associations differed between males and females. These results suggest the need for interventions to reduce smartphone addiction among undergraduate students.

State-of-the-art low-power-level metal-oxide-semiconductor field-effect transistor (MOSFET)-based transformerless photovoltaic (PV) inverters can achieve high efficiency by using latest super junction MOSFETs. However, these MOSFET-based inverter topologies suffer from one or more of these drawbacks: MOSFET failure risk from body diode reverse recovery, increased conduction losses due to more devices, or low magnetics utilization. By splitting the conventional MOSFET-based phase leg with an optimized inductor, this paper proposes a novel MOSFET-based phase leg configuration to minimize these drawbacks. Based on the proposed phase leg configuration, a high efficiency single-phase MOSFET transformerless inverter is presented for the PV microinverter applications. The pulsewidth modulation (PWM) modulation and circuit operation principle are then described. The common-mode and differential-mode voltage model is then presented and analyzed for circuit design. Experimental results of a 250 W hardware prototype are shown to demonstrate the merits of the proposed transformerless inverter on nonisolated two-stage PV microinverter application.

Chinese citizens regularly experience some form of bodily pain, yet little is known regarding the epidemiology of pain. We conducted a nationally representative sample cross sectional study to estimate the prevalence of pain and identify risk factors of pain among 19,665 community residents aged 18–65 years in China. The China Sub-optimal Health Survey (CSHS) data was used to estimate pain prevalence. Body pain was also estimated by self-reports from the sample population. A logistical regression model was applied to estimate the odds ratio and 95 % CIs of acute pain and chronic pain to explore the potential risk factors. Women had a higher prevalence of pain than men (39.92 vs. 32.17 % for chronic pain). The prevalence of pain increased with age (29.72 % for ages 18–25 vs. 42.23 % for ages 45–65). The most common complaints were head, neck/shoulder, and waist/back pain. Females (OR 1.57, 95 % CI 1.44–1.71) ages 25 or older (25–45: OR 1.19, 95 % CI 1.04–1.36; 45–65: OR 1.47, 95 % CI 1.26–1.73) were more likely to report having chronic pain. Subjects’ living areas, and their drinking status (OR 1.32, 95 % CI 1.13–1.53) or smoking status (OR 1.01, 95 % CI 0.91–1.11), were also factors that were significantly associated with increased reporting of chronic pain. Women had a higher prevalence of chronic pain than men, although both sexes had a high prevalence for chronic pain. There were significant differences between the two sexes and the location of chronic pain in the body, most notably in the shoulders, stomach, abdomen, and waist.

Driven by worldwide demands for renewable energy source, photovoltaic (PV) inverters, which are the most important part for energy conversion, have seen a considerable amount of innovations in recent years. The trends for PV inverters are toward high efficiency, high reliability, low ground leakage current, low-output ac-current distortion, and reactive power capability. This paper provides an efficiency optimized design of an Auxiliary Resonant Snubber with Coupled-Magnetic Reset Zero-voltage switching (ZVS) inverter for PV application. The main device is Power MOSFETs, which have low conduction loss and could achieve ZVS in all load condition. The auxiliary devices are low current, low cost IGBTs and Diodes, which could achieve zero-current switching (ZCS). To achieve high efficiency, resonant circuit is analyzed to optimally design the resonant components, which is based on the guarantee of full range ZVS, gating delay-time design, and lower power loss in auxiliary circuit. The power loss model is also analyzed to select suitable power device and further improve the efficiency. At last, experiment results of a 5kW single phase inverter in PV system was presented, which has more than 99% CEC efficiency and work in full load condition without cooling fan. Besides, reactive power capability is also demonstrated.

This paper presents a new method of current control that employs burst mode in order to balance the dc-side capacitor voltages of split phase inverters. By alternating the inductor current in every switching period, zero-voltage switching (ZVS) can be achieved, which avoids the reverse recovery issue of power MOSFETs. As a result, super-junction MOSFETs instead of IGBTs can be employed to achieve higher efficiency. Combining the hysteresis current control with traditional pulse-width modulation (PWM), a new burst mode control method is proposed in this paper. The minimum operation time during a set modulation period is limited then the efficiency at the light load can be increased. A buck-and-boost converter is employed as the auxiliary circuit for the capacitor voltage balancing circuit. Due to the proposed ZVS method, inductor volume can be reduced. A prototype with 25 A current capacity is built to verify all the performance of the presented control method. The efficiency over the whole load range is over 98% with a peak efficiency of 98.4%.

Unsafe injection practices significantly increase the risk of human immunodeficiency virus (HIV) infection among injection drug users (IDUs). Little is known about how demographic characteristics of IDUs are linked to HIV-related risk behaviors in the central regions of China. A cross-sectional survey was conducted at Mandatory Detoxification Centers (MDCs) and the community in Maanshan, China. Of the 916 IDUs, 96.4 % reported a history of heroin use during the past year, 93.4 % had HIV/AIDS knowledge, 16.8 % reported receptive syringe sharing and 12.2 % reported inconsistent condom use in commercial sex in the past year. Unsafe injection practice was associated with increased odds of minority ethnicity, lower level of education, and no peer education in the past year. Unsafe sex practice was associated with increased odds of being single, 18–30 years of age, non-local residence, and history of methamphetamine use in the past year. Integrated interventions to promote safe injection and protected commercial sex practices targeting IDUs must also consider individual and socio-environmental factors.